Suitability of Pea Starch and Calcium Alginate as Antimicrobial Coatings on Chicken Skin

The effect of incorporating trisodium phosphate (TSP) in pea starch (PS) and acidified sodium chlorite (ASC) in calcium alginate upon the antimicrobial activity of TSP and ASC was studied against a 3-strain cocktail of Salmonella inoculated on chicken skin. The influence of polymer coating concentration on skin pH, coating-skin adhesion, and coating absorption upon antimicrobial performance were investigated. Aqueous solutions of 0.5 to 4.8% (wt/vol) PS were prepared with 10% (wt/vol) TSP (PS + TSP coating), and alginate + ASC coatings contained 1% (wt/vol) calcium chloride in 1,200 ppm of ASC mixed with an aqueous solution of 0.5, 1.0, or 1.5% (wt/vol) sodium alginate. Coating drops (10 microL) were placed on chicken skin thighs, and the angle formed by the tangent of the liquid surface at the skin interface (contact angle) was measured using a digital camera to assess coating-skin adhesion. Excised skins were mounted in a ring holder, and 5 mL of the coatings was applied to the skin. Weight changes in the skins that were related to coating absorptiveness were recorded. The TSP dissolved in 3.5% PS and ASC in 1% alginate reduced Salmonella by 1.6 log cfu/g and 1.4 log cfu/g, respectively, within 24 h. These reductions were significantly greater than those caused by TSP or ASC alone in water for up to 120 h. In coatings, TSP and ASC caused significant elevation or reduction of skin surface pH for up to 120 h, respectively. The TSP destabilized PS with 88% of the coating having dripped from the skin 1 h later. Coatings with 0.5% PS were absorbed quickly by the skin and had high skin adhesion, whereas those with >3.5% PS had low skin adhesion and slow absorption. Alginate coatings with or without ASC were stable, and about 50% of the coating weight was retained at 120 h. The latter coatings appeared to have low absorptiveness because the skin gained approximately 1.0% of its weight within 60 min following application. These findings indicate that effects of the agents in coatings on skin pH, the extent of coating adhesion, and absorption may contribute to overall antimicrobial behaviors.